Combustion microwave diagnostic system

ABSTRACT

Methods to resonate the combustion chamber of internal combustion engines at radio frequencies, for the purpose of bottom dead center measurement at all available engine rpm are disclosed. Methods to employ the Q value of radio frequency resonances in combination with electron producing standard fuels for mechanical and electrical measurements within and near the combustion chamber, at all available rpm, are also disclosed. The basic system employed in the measurements comprises a turnable source of coherent radio frequency energy and a hybrid transmission line to convey the radio frequency energy into the combustion chamber. It is also used to detect the energy reflected back from the combustion chamber. The method for detecting bottom dead center requires changing the transmitted frequency so that a resonance occurs at precisely the maximum displacement of the piston during it&#39;&#39;s stroke. The method for determining the properties of materials requires a comparison between the Q value with standard electron producing fuel and the Q value of the ingredients in question.

United States Patent Merlo [451 Nov. 28, 1972 COMBUSTION MICROWAVEDIAGNOSTIC SYSTEM Angelo Louis Merlo, Long Lake Road, Troy, 48084 Filed:April 27, 1971 Appl. No.: 137,780

2115 East Mich.

Inventor:

Related US. Application Data US. Cl. ..73/116, 324/585 C Int. Cl. ..G0lm15/00 Field of Search ..73/116, 35; 324/585 C References Cited UNITEDSTATES PATENTS 11/1960 Linberg, Jr ..73/116 UX 9/1960 Bodine ..73/116 UXPrimary Examiner-Jerry W. Myracle ABSTRACT Methods to resonate thecombustion chamber of internal combustion engines at radio frequencies,for the purpose of bottom dead center measurement at all availableengine rpm are disclosed. Methods to employ the Q value of radiofrequency resonances in combination with electron producing standardfuels for mechanical and electrical measurements within and near thecombustion chamber, at all available rpm, are also disclosed. The basicsystem employed in the measurements comprises a tumable source ofcoherent radio frequency energy and a hybrid transmission line to conveythe radio frequency energy into the combustion chamber. It is also usedto detect the energy reflected back from the combustion chamber. Themethod for detecting bottom dead center requires changing thetransmitted frequency so that a resonance occurs at precisely themaximum displacement of the piston during its stroke. The method fordetermining the properties of materials requires a comparison betweenthe Q value with standard electron producing fuel and the Q value of theingredients in question.

7 Claim, 3 Drawing Figures 6 I3 9 l J H .r mmmm x IO Q 2 t l Q PATENTEDNOV 2 8 I972 SHEET 2 [IF 2 F IG'. 2 A

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INVENTOR COMBUSTION MICROWAVE DIAGNOSTIC SYSTEM This invention is aContinuation-in-part of my application, Ser. No. 764,566 filed Oct. 2,1968, now U. S. Pat. No. 3,589,177.

This invention relates to a diagnostic system for the combustion chamberof internal combustion engines, and to means for using electromagneticradiant energy in the ultra high and microwave frequency range to senseand measure the movement and behavior of parts as well as combustionphenomenon within the combustion chamber during high speed operation ofengines. In more particular it relates to a novel method to detect thetime of bottom dead center of the piston stroke of an internalcombustion engine by means of a microwave resonance and it also relatesto methods to employ resonances to study ingredients that develop duringthe combustion process.

The combustion chamber of an internal combustion engine is a hot andhostile environment and previous methods to perform dynamic measurementswithin the combustion chamber during high speed engine operation havenecessitated the use of elaborate and carefully adjusted equipment. Incertain cases it has been necessary to modify the engine in order forexperiments to be performed, therefore past methods have not gainedwidespread use.

It is an object of this invention to provide a convenient means tomeasure the high speed chemical ionization reactions taking place duringthe combustion cycle by employing the Q value of resonances, withoutmodifications to engines.

Another object of this invention is to provide means to utilize theelectromagnetic energy resonance phenomenon within the combustionchamber to monitor high speed mechanical displacements.

Another object of this invention is to provide the means whereby highspeed moving parts within the combustion chamber may be trackedelectronically by employing the electromagnetic energy resonances.

Another object of this invention is to provide, through the use ofresonances, the means to measure the time of Bottom Dead Center and bythe employment of this measurement the means also to measure the time ofTop Dead Center during high speed engine operation.

Another object of this invention is to provide the methods for referencestandards of microwave resonance measurements by employing standardelectron producing tracer fuels in the combustion chamber.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which:

FIG. I is a general diagram of the apparatus.

FIG. 2A shows the nature of the microwave video detected resonance atlow excitation frequency.

FIG. 2B shows the nature of the microwave resonance when occurring atthe turn around point at the bottom of the piston stroke correspondingto maximum piston displacement.

While the invention is susceptible of various modifications andalternative arrangements, I have shown in the drawings and will hereindescribe in detail the preferred embodiments. It is to be understood,however, that I do not intend to limit the invention by such disclosurefor I aim to cover all modifications and alternative arrangementsfollowing within the spirit and scope of the invention as in theappended claims.

FIG. 1 shows a general view of the apparatus. The spark plug 1 is shownenclosed by a cylindrical shield 2 which forms the outer conductor of acoaxial transmission line operating in the TEM mode. The subject ofresonances is discussed on page of the book titled UnderstandingMicrowaves, John F. Rider Publisher, Victor Young Author, published inNew York. The definition of modes can be found in the Waveguide HandbookMIT Rad. Lab. Series Volume 10, edited by N. Marcuvitze, copyright 1951by Mc- Graw Hill Book Co. Inc., also in the Microwave Engineers Handboodpublished by Horizon House- Microwave Inc., 196I-l962, pages TD-25 toTD-32, and also pages TD-74 and TD-75. Electromagnetic energy passesthrough this coaxial line in the process of entering the combustionchamber 3 which is a cylindrical enclosure forming an electromagneticwave cavity. This cavity, which is also the combustion chamber, istumable by virtue of the motion of the piston 4 within the cylinder wall5. The coaxial transmission line having cylindrical outer conductor 2 inFIG. 1 utilizes a low loss dielectric filling between the outer 2 andinner 6 conductor. This dielectric filling is exposed 7 at the top endand forms an effective ignition spark insulator to ground for theignition lead 8. Electromagnetic energy generated by the source 9 entersa rectangular waveguide section 10 through the coax to waveguide adapter11. This energy moves within the waveguide section 10 to the coaxsection 2. A portion also passes beyond coax section 2 to theelectromagnetic energy detector 12 to bias this device into its mostsensitive operating range. A very small portion escapes throughinsulator 7. The portion which escapes through insulator 7 is minimizedby construction of this part of the coax section to have a highimpedance to the flow of energy. This is accomplished by increasing theratio formed by the outer diameter of the coax divided by the diameterof the center conductor 6. In FIG. 1 the electromagnetic energy source 9has been selected to be a reflex klystron, this invention is notrestricted to this type of electromagnetic energy source. The reflexklystron, however, is a convenient source for frequency and amplitudetypes of modulation through the klystron power supply 13 which suppliesbiasing potentials to the klystron 9.

As the piston moves up and down within the cylindri- I cal chamber 5,predictable electromagnetic energy resonant absorptions occur. Theseabsorptions appear at the detector 12 as amplitude variations ofdetected energy. As the piston 4 proceeds from the extreme top of thestroke towards the extreme bottom of the stroke, absorptions due to theTE, TM TE etc. modes appear according to a well established theoryconcerning this electromagnetic phenomenon. The resonances occur forparticular positions of the piston, dependent upon the geometry of thechamber, the frequency of the electromagnetic energy and the dielectricconstant and loss tangent of the dielectric materials existing withinthe chamber 3. Properties of the dielectric material existing in thechamber and interacting with the resonance can be determined bymeasuring the Q of the resonance. This technique is described, forexample, by F. l-Iorner et al., Resonance Method of DielectricMeasurement at Centimeter Wavelengths. .I. IEE, volume 93, Pt. III pp.5358, January 1946. The use of this technique was disclosed inconnection with the resonances excited within combustion chambers ofinternal combustion engines in a paper presented at the 2" AnnualTransducer Conference held at the National Bureau of Standards,Gaithersburg, Md. on May 5, 1970, and published in the IEEE Transactionson Industrial Electronics and Control Instrumentation April I970 volumeIECI-l7 Number Two, which first became available to subscribers on May4, 1970, the first day of the meeting. The title of the presentation andthe subsequent publication is Combustion Chamber Investigations By Meansof Microwave Resonances by the applicant of this invention.

The absorptions within the combustion chamber 3 appear as variations inthe voltage at the detector 12. The pre-amplifier 14 is utilized toincrease the magnitude of the voltage which appears from the detectorand also to institute filtering of the signals that appear from thedetector with regards to the frequencies which are magnified and whichare permitted to pass.

FIG. 2A shows the character of a typical resonance, the TE as it can beobserved using an oscilloscope connected to the output of thepre-amplifier 14 during the operation of the engine.

The position of occurrence in time of the resonance with respect to thetime of occurrence of top dead center is determined by the geometry ofthe cylinder, the frequency of the exciting energy and the contents ofthe combustion chamber. The same argument holds for the time ofoccurrence of bottom dead center. The phase of the absorption signalwith respect to time, as seen by the oscilloscope depends upon thedirection of travel of the piston. If the resonance occurs displaced intime from the time of bottom dead center of the piston travel, 180degree phase reversals exist in the resonance between ascending anddescending directions of piston travel. Observation of the phase of theresonance is therefore indicative of the direction of piston motion. Thetime of occurrence of the resonance with respect to the time ofoccurrence of bottom dead center can be shortened by decreasing theradiated frequency. As the magnitude of the of the radiated frequency isreduced, a value of frequency will be reached in which the piston can nolonger change the dimensions of the combustion chamber sufficiently tomove completely through the resonance. This condition is shown by FIG.2B. The combustion chamber therefore remains in the resonant conditionas the piston proceeds around bottom dead center. If the Q value of theresonance is high, the resonance will occupy very small increments ofpiston displacement. The smaller the increment in piston displacementoccupied by the resonance the greater will be the resolving power ofthis technique to detect small changes in the displacement of thepiston. When the frequency is selected to cause the resonance to occurat bottom dead center and the Q value is high, the time of occurrence ofbottom dead center can be determined with accuracies corresponding tobetter than one degree of angular piston displacement.

The magnitude of the Q of the resonance is indicative of the number ofcharged particles existing within the combustion chamber during the timethat the resonance is occurring. A high 0, representing a resonanceoccupying small increments of angular piston displacement, results whena minimum of charged particles exist within the resonating combustionchamber. The resonances excited within a combustion chamber in theabsence of fuel and ignition is a reference condition for themeasurement of the number of existing charged particles. The addition offuel containing Cesium or other electron producing ingredients incalibrated quantities serves as another means to determine the number ofcharges being measured by the resonances.

What is claimed to be new, novel and inventive by this disclosure is asfollows I claim:

1. The method of measuring the time of occurrence of bottom dead centerof the angular displacement of the piston of an internal combustionengine at all available rpm comprising the steps of generating anexternally controlled ultra high and microwave radio frequency wave,radiating said wave into the combustion chamber of said engine,detecting a resonance of said wave reflected from said chamber, changingthe wavelength of said wave to cause the overlap in time of the selectedresonance mode excited by the piston moving in the down direction withsaid same mode excited by said piston moving in the up direction, timeof said overlap then being coincident with the time of bottom deadcenter, and essentially placing said resonance at the point of maximumdisplacement of said piston at its turn around point.

2. The method according to claim 1 wherein the resonance mode employedis the TB mode, said mode having resonant frequency dependent upon threedimensions, said mode resonating at only one displacement of the pistonof internal combustion engines, said mode having electric fieldperpendicular to axis of cylinder of said engines, said electric fieldhaving terminations on charges existing on opposite walls of thecylinder, said mode having conduction currents existing in the walls ofsaid cylinder, said conduction currents traversing said pistons contactwith said cylinder wall completing paths to said charges, said electricfield surrounded by circular magnetic field.

3. The method according to claim 1 wherein the time of occurrencebetween successive bottom dead centers is employed to be divided in two,in order to identify the time of top dead center.

4. The method of measuring the number of charged particles within thecombustion chamber of an internal combustion engine at all availablerpm, comprising the steps of generating an externally controlledcoherent ultra high and microwave radio frequency wave into said chamberof said engine, detecting a particular resonance of said wave reflectedfrom said chamber, measuring the Q value of said resonance, comparingsaid Q value with the Q value of the said resonance excited in thepresence of standard fuel containing a calculated predetermined quantityof charged particles.

5. The method according to claim 4 wherein the comparison standard is acombustion chamber containing an absence of any fuel and ignition.

6. The method according to claim 5 wherein the resonance mode is the TMmode, said mode having constant field strength in two dimensions, saidmode having resonant frequency dependent only upon one dimension, saiddimension being the radius of the cylinder, said mode remaining inresonance throughout all values of displacement of the piston ofinternal combustion engines, said mode having electric field coincidentwith the axis of the cylinder of said engines, said electric fieldhaving terminations on charges existing on center of said piston andalso on the opposite end of said cylinder, said mode having conductioncurrents existing in the walls of said cylinder, said conductioncurrents traversing said pistons contact with said cylinder wallcompleting paths to said charges, said axial electric field surroundedby circular magnetic field.

7. The method according to claim 4 wherein the resonance mode is the TMmode, said mode having constant field strength in two dimensions, saidmode having resonant frequency dependent only upon one dimension, saiddimension being the radius of the cylinder, said mode remaining inresonance throughout all values of displacement of the piston ofinternal combustion engines, said mode having electric field coincidentwith the axis of the cylinder of said engines, said electric fieldhaving terminations on charges existing on center of said piston andalso on the opposite end of said cylinder, said mode having conductioncurrents existing in the walls of said cylinder, said conductioncurrents traversing said pistons contact with said cylinder wallcompleting paths to said charges, said axial electric field surroundedby circular magnetic field.

1. The method of measuring the time of occurrence of bottom dead centerof the angular displacement of the piston of an internal combustionengine at all available rpm comprising the steps of generating anexternally controlled ultra high and microwave radio frequency wave,radiating said wave into the combustion chamber of said engine,detecting a resonance of said wave reflected from said chamber, changingthe wavelength of said wave to cause the overlap in time of the selectedresonance mode excited by the piston moving in the ''''down''''direction with said same mode excited by said piston moving in the''''up'''' direction, time of said overlap then being coincident withthe time of bottom dead center, and essentially placing said resonanceat the point of maximum displacement of said piston at its turn aroundpoint.
 2. The method according to claim 1 wherein the resonance modeemployed is the TE111 mode, said mode having resonant frequencydependent upon three dimensions, said mode resonating at only onedisplacement of the piston of internal combustion engines, said modehaving electric field perpendicular to axis of cylinder of said engines,said electric field having terminations on charges existing on oppositewalls of the cylinder, said mode having conduction currents existing inthe walls of said cylinder, said conduction currents traversing saidpistons contact with said cylinder wall completing paths to saidcharges, said electric field surrounded by circular magnetic field. 3.The method according to claim 1 wherein the time of occurrence betweensuccessive bottom dead centers is employed to be divided in two, inorder to identify the time of top dead center.
 4. The method ofmeasuring the number of charged particles within the combustion chamberof an internal combustion engine at all available rpm, comprising thesteps of generating an externally controlled coherent ultra high andmicrowave radio frequency wave into said chamber of said engine,detecting a particular resonance of said wave reflected from saidchamber, measuring the Q value of said resonance, comparing said Q valuewith the Q value of the said resonance excited in the presence ofstandard fuel containing a calculated predetermined quantity of chargedparticles.
 5. The method according to claim 4 wherein the comparisonstandard is a combustion chamber containing an absence of any fuel andignition.
 6. The method according to claim 5 wherein the resonance modeis the TM010 mode, said mode having constant field strength in twodimensions, said mode having resonant frequency dependent only upon onedimension, said dimension being the radius of the cylinder, said moderemaining in resonance throughout all values of displacement of thepiston of internal combustion engines, said mode having electric fieldcoincident with the axis of the cylinder of said engines, said electricfield having terminations on charges existing on center of said pistonand also on the opposite end of said cylinder, said mode havingconduction currents existing in the walls of said cylinder, saidconduction currents traversing said pistons contact with said cylinderwall completing paths to said charges, said axial electric fieldsurrounded by circular magnetic field.
 7. The method according to claim4 wherein the resonance mode is the TM010 mode, said mode havingconstant field strength in two dImensions, said mode having resonantfrequency dependent only upon one dimension, said dimension being theradius of the cylinder, said mode remaining in resonance throughout allvalues of displacement of the piston of internal combustion engines,said mode having electric field coincident with the axis of the cylinderof said engines, said electric field having terminations on chargesexisting on center of said piston and also on the opposite end of saidcylinder, said mode having conduction currents existing in the walls ofsaid cylinder, said conduction currents traversing said pistons contactwith said cylinder wall completing paths to said charges, said axialelectric field surrounded by circular magnetic field.